FIG. 1 depicts a swimming pool, and the problem concerned.
A swimming pool 12, while not being used, must be covered by a cover 18, for protecting of the accidental entrance of children and the like while the swimming pool is not guarded, and prevention of accidental drowning.
However, children might enter by creating an opening of the pool cover 14a that allows entering the pool.
The conventional solution to the problem is by video means or by motion sensor. However, without super quality and expensive means, these solutions provide false alarms, as they can alert also in other irrelevant cases and not just focused to the case to be indicated.
US20130313204 discloses light sensors to determine whether an spa is covered or not.
However, US20130313204 does not provide a solution for alerting upon presence of one of various local/partial openings 14a of pool cover 18.